Gas turbine components such as nozzles are subjected to intense heat and external pressures in the hot gas path. These rigorous operating conditions are exacerbated by advances in the technology, which may include both increased operating temperatures and greater hot gas path pressures. As a result, components such as nozzles are sometimes cooled by flowing a fluid through a manifold inserted into the core of the nozzle, which exits the manifold through impingement holes into a post-impingement cavity, and which then exits the post-impingement cavity through apertures in the exterior wall of the nozzle, forming a film layer of the fluid on the exterior of the nozzle.
The materials from which turbine components such as nozzles are formed, combined with the particular conformations which the turbine components include, lead to certain inhibitions in the cooling efficacy of the cooling fluid systems. With respect to nozzles, by way of example, the external surface of the nozzle may include a sharply narrowing conformation, which the manifold must follow. However, the narrowing conformation of the nozzle and the structural limitations of the materials used to form the manifold inserted into the nozzle may lead to the formation of an enervated zone in the portion of the post-impingement cavity closest to the trailing edge of the nozzle. The material of the manifold can only be turned to a particular degree of bend radius without compromising the structure integrity of the manifold, which limits how far along the narrowing nozzle the manifold can project, and thereby limits how close impingement holes can be positioned into the most tapered portion of the nozzle. The lack of impingement holes in this enervated region decreases the cooling effect of the cooling fluid, as the cooling fluid will circulate less in the enervated zone. The presence of this enervated zone either requires excess cooling fluid to be employed, reducing overall efficiency of the turbine, or limits the temperature at which the turbine can operate, also reducing overall efficiency of the turbine.